A bovine tubercle bacillus attenuated BCG strain (Mycobacterium bovis BCG, hereinafter referred to as “BCG”) has been known as the most common live bacteria vaccine because of its safety.
On the other hand, as gene recombinant technologies have been keenly developed and improved for the past ten plus years, there have been many studies for modifying microorganisms such as viruses and bacteria to produce a foreign antigen protein and using them as vaccine vectors for preventing and treating various kinds of infectious diseases and cancers. Regarding BCG, for example, recombinant BCG vaccines targeted to human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) have been also reported (J. Immunol. 164: 4968-4978, 2000, J. Virool. 71: 2303-2309, 1997, and Infect Immun. 57: 283-288, 1989).
The BCG strain is considered as a candidate for providing an excellent recombinant vaccine because of its safety and easy supply. However, the conventional recombinant BCG vaccine has not always been sufficient in its capability of inducing immunity to infection, cancer, or the like to be provided as a target. For example, in the case of immunizing a guinea pig with a recombinant BCG vaccine targeted at HIV-1, it should be dosed 10 to 100 times higher than a typical dosage (0.05 to 0.1 mg) of BCG vaccine generally used for human (Proc. Natl. Acad. Sci. USA. 92: 10698-10697, 1995).
On the other hand, in the recombinant vaccine, as means for providing a foreign antigen with high immunogenicity, the optimization of codon is attempted. Those are, the codon optimizations, such as listeriolysin O of Listeria monocytogenes (J. immunol 161: 5594-5599, 1998), HIV-1 Gag (J. Virol. 75: 10991-11001, 200; J. Virol. 74: 2628-2635, 2000), Env (J. Virol. 72: 1497-1503, 1998), tetanus toxin (Vaccine 19: 810-815, 2000), L1 protein of human papilloma virus (J. Virol. 75: 9201-9209, 2001), merozoite surface protein 1 of falciparum malaria protozoan (Plasmodium falciparum) (Infect. Immun. 69: 7250-7253, 2001). However, these codon optimizations are those obtained by humanized codons for each amino acid of antigens. In addition, those recombinant vaccines are also DNA vaccines (naked DNA), so that there is no report at all about effects of the codon optimization in vaccine predominantly composed of other recombinant vector of BCG strain or the like.
The invention of the present application has performed in consideration of circumstances described above, and addresses to provide a recombinant BCG vaccine which is excellent in the expression amount of an antigenic protein and, as a consequence, capable of inducing a sufficient immune response to the target infectious disease, cancer, or the like even though the dosage thereof is almost equal to that of typical BCG vaccine.